What is wrong with this git smudge/clean filter?

Question

I want to apply this filter in my git repository to remove a section from a solution file during checkout and to add this section during commit.

This is the section i want to remove or add:

GlobalSection(SubversionScc) = preSolution
    Svn-Managed = True
    Manager = AnkhSVN - Subversion Support for Visual Studio
EndGlobalSection

I have setup this filter in my .git/info/attributes

*.sln filter=SourceControlProvider

and i have added these commands to my config

$ git config filter.SourceControlProvider.smudge "sed -e '/GlobalSection(SubversionScc)/,/EndGlobalSection/d' %"
$ git config filter.SourceControlProvider.clean "sed -n -e '/^Global$/ r ankhsvnsection ' < %"

Well, it does not work. What have i done wrong?

ankhsvnsection is a text file that lies in the same directory as the *.sln file

Answer 1

I see a few issues here:

1. You have % at the end of both filters.
   This has no special meaning and will be passed as an extra argument to sed, which will probably generate an error (unless you have a file named %).
   Filters should be “streaming” (read from stdin and write to stdout). Their definition can include %f, but it should not really be treated as a file to read or write; Git does that part, filters should just read from stdin and write to stdout.

2. Your clean filter tries to redirect stdin from %f.
   The input data will already be on stdin, there is no need to redirect.

3. The sed program in the clean filter uses the r command to access another file.
   Filters seem to be run from root of the working tree, but I am not sure if that is guaranteed.

4. The sed command in the clean filter uses -n. Its only output will be the contents of the ankhsvnsection file (assuming the input has a Global line).

5. Some versions of sed (at least the (old) BSD version in Mac OS X) do not allow whitespace after the filename of the r command (i.e. the space after ankhsvnsection in the clean filter’s sed program).

After adding, changing, or removing a filter you will probably need to touch, modify, or delete your working tree files before Git will apply the filter. Git’s index records the modification time of working tree files; if they have not changed, then Git will translate git checkout -- file and git add file into a no-op.

If you want to see the actual contents of the index (e.g. to check what the clean filter produced), you can use git show :0:path/from/repo/root/to/file. You can not usually use git diff for this since it also applies the filters.

These worked for me:

git config filter.SourceControlProvider.smudge "sed -e '/GlobalSection(SubversionScc)/,/EndGlobalSection/d'"
git config filter.SourceControlProvider.clean "sed -e '/^Global\$/ r ankhsvnsection'"